Inductor



Feb. 7, 1967 Filed June 23, 1964 H. KUHLBARS INDUCTOR 2 Sheets-Sheet 1H. KUHLBARS Feb. 7, 1967 INDUCTOR 2 Sheets-$heet 2 Filed June 23, 1964Jn van for 6,;

United States Patent Ofifice Patented Feb. 7, 1967 2 Claims. c1: 21910.4s)

The invention relates to an inductor for heat treating workpiece facesmeeting at an angle.

It is already known that inductors may be constructed roughly to conformwith the contours of the work they are intended electro-inductively toheat. This applies irrespectively as to whether it is desired to heatexclusively the surface or the entire cross section of the work.However, particularly in cases in which the heating operation forms partof a surface treatment, for instance for hardening the surface,difliculties arise in producing a suitable temperature distribution inthe work at points where two workpiece faces angularly meet. For dealingwith this situation the inductor is constructed to make a matching angleat such a corner, but the distribution of the current in the crosssection of the conductor at the corner then tends to be such that anadequate intensity of the heat supplying sources and hence the requiredheating effect in the region of the vertex of the angle in the workpieceis not produced.

As known, it has already been proposed to remedy this defect byproviding magnetic yokes made of laminar iron sheet. However, where aconductor makes a sharply angled corner such laminations cannot besuitably mounted to produce a satisfactory effect which extends wellinto the actual corner in the work. This phenomenon is connected withthe fact that on the inside of an angle in the conductor there is lessroom for mounting laminations than on the outside of the angle.

It is the object of the present invention to provide an inductor whichwill have a penetrating heating effect even in corners where twoworkpiece faces make an angle. According to the invention this isachieved by mitre cutting the conductor at the corner and electricallyjoining the mitred ends only at the outside vertex of the mitre angle.This brings about a concentration of the field lines in the corner andthus intensifies the field sufficiently to produce a penetrating thermalefiect into the workpiece corner, exceeding that which known angularinductors can provide.

In a preferred arrangement the mitred joint is filled with an insulatingmaterial to provide the required mechanical strength. The electricalconnection is formed by welding a wire across the joint. Convenientlythe hollow conductor sections are of the twin chambered type, thecentral web being perforated at the joint.

In the drawings FIG. 1 is a view of a workpiece in association with aconventional inductor,

FIG. 2 is a view of an inductor according to the invention, whereas FIG.3 is a fragmentary part sectional perspective view of the proposedinductor.

Assuming that the problem is to surface harden a corner region 2 in aworkpiece 1, then the inductor would have effective sections marked 3 inFIG. 1 and the inductor would be moved across the surface of the work ina direction normal to the plane of the paper. The effective sections 3of the inductor form an angle at 4. Their ends are therefore mitred insuch a way that the resultant angle conforms with the corner region 2 ofthe workpiece 1. If it is now desired to heat and hence to harden asurface zone defined by the line at 5, then this cannot be done with aninductor of the kind shown in FIG. 1. The hardened zone which isactually achieved with this inductor has the shape indicated by thedotdash line at 6.

This shape of hardened Zone can be improved to conform a little betterwith the shape of the desired hardened Zone, as defined by 5 and toassume the shape indicated by the chain line 13, if laminar yokes 7 aremounted on the inductor. However, a hardened zone of the desired shapeis not achieved.

The invention permits this to be remedied by leaving a gap 9 between themitred ends of the two inductor sections. A copper wire 10 welded orsoldered across the joint at the vertex of the angle formed by the mitrecuts provides the necessary electrical connection between the inductorsections. Conveniently the gap in the mitred joint 9 is filled with aninsulating material suitable for imparting the necessary mechanicalstrength to the joint. The effect of this inductor can now be quitesubstantially further improved by mounting magnetic yokes 7 on thesections 8 in the same way as shown in FIG. 1.

As known, inductors usually require cooling. To this end the sections 8of the inductor have the form of twin chambered sections, the dividingweb 11 being perforated in the region of the mitre cut 9, as indicatedat 12. The liquid coolant can thus flow from one chamber into the other.

What I claim is:

1. An inductor for heat treating an angular workpiece comprisingangularly arranged conductor portions having opposed end mitre faceselectrically connected only in the region of the outer vertex of themitre angle and comprising a wire forming the said electrical connectionand being welded across the said end mitre faces and insulating materialfilling the said gap between the said faces.

2. An inductor for heat treating an angular workpiece comprisingangularly arranged conductor portions having opposed end mitre faceselectrically connected only in the region of the outer vertex of themitre angle, said conductor portions being hollow and being eachprovided with an internal partition forming twin longitudinal chamberstherein, said partition being perforated in the region of the mitrejoint.

References Cited by the Examiner UNITED STATES PATENTS 2,810,05310/1957. Messner 219-1079 X 2,810,054 10/1957 Jones 21910.79 X

RICHARD M. WOOD, Primary Examiner.

L. H. BENDER, Assistant Examiner.

1. AN INDUCTOR FOR HEAT TREATING AN ANGULAR WORKPIECE COMPRISINGANGULARLY ARRANGED CONDUCTOR PORTIONS HAVING OPPOSED END MITRE FACESELECTRICALLY CONNECTED ONLY IN THE REGION OF THE OUTER VERTEX OF THEMITRE ANGLE AND COMPRISING A WIRE FORMING THE SAID ELECTRICAL CONNECTIONAND BEING WELDED ACROSS THE SAID END MITRE FACES AND INSULATING MATERIALFILLING THE SAID GAP BETWEEN THE SAID FACES.